Cloning animals by nuclear transfer of somatic cells is a scientifically important topic that is also politically charged. It is therefore imperative for rigorous experimentation to inform both the scientist and the public at large, and that the work be conducted with the highest standards of care, control and understanding. The goal of this proposal is to investigate an undesirable side effect of the cloning process, obesity, using a mouse model. We have found that the obese phenotype is maintained over successive generations of cloned mice;i.e. clones derived from clones, but it is not passed through the germ line to naturally derived offspring, suggesting that the obese phenotype of cloned mice is an epigenetic rather than a genetic phenomenon. Proposed experiments will begin to explore possible mechanisms for the obesity in cloned mice. Specific Aims are: 1) To determine whether obesity in cloned mice is the result of hyperphagia or differences in metabolic rate during early postnatal development. We hypothesize that cloned mice are hyperphagic and/or have lower energy expenditure and metabolic rate early in development relative to controls;2) To test the hypothesis that obese clones defend their elevated body weight comparably to other obese animals, and to identify components of the neuroendocrine control system of energy homeostasis that are altered in clones;and 3) To test the hypothesis that increased body weight and obesity in cloned (and in vitro-manipulated control mice to a lesser extent) result from in vitro embryo production and/or in vitro mechanical manipulation. Collectively, these experiments will provide detailed information about clones as well as the long-term effects of the process used to generate the clones. To accomplish this, we have put together a team of authorities on the cloning process itself (Yanagimachi and Yamazaki), on obesity (Woods), and on assessment of the requisite behavioral, physiological, endocrine and neurobiological parameters (Sakai). Investigators at the University of Hawaii (UH) who pioneered the nuclear transfer technique will generate the cloned mice as well as the control animal groups. The group at the University of Cincinnati (UC) will conduct behavioral, physiological and neurochemical studies to phenotype the cloned mice and their controls. The proposed research will provide the first set of longitudinal studies in cloned mice that examine the long-term consequences of somatic cell cloning. In addition, the behavioral, physiological, and neurochemical data obtained will enhance our understanding of the mechanisms of obesity, a serious and growing chronic public health issue worldwide.